Physics Chp 9

• Fluids – move (flow), change shape

• Liquids vs Gases

• Density p = m/V

• Density of water is 1000 kg/m3

• Why do you feel lighter in a pool?

• Buoyant Force

• FB = mfg

• FB = pfVfg

• FB = mog

• So our weight in water

• Fnet = Fg – FB

• Fnet = mg - pVg

• If submerged in a fluid

• Fg/FB = po/pf

• Pressure

• P = F/A

• In a closed system P is constant

• P1 = P2 F1/A1 = F2/A2

• Jacks use this equation

• The force you put in on an area comes out the other end and if the area is large the force also has to be large to have a constant pressure.

• As you dive down in a pool the pressure increases, why?

• P = Po + pgh

• How does this also explain the problem with climbing Mt. Everest?

• P = 101325 Pa + (1.29 Kg/m3 )(9.8 m/s2)(-8850m)

• P =

• How does this affect cooking?

• Temperature

• Celsius vs Kelvin

• K = oC + 273

• As fluid enters a tube that is open on both ends the mass of the fluid going in has to be equal to the mass coming out.

• A1v1 = A2v2 continuity equation

• How does this explain the effect on kinking a hose?

• Bernoulli’s Equation

• P1 + 1/2pv12 + pgh1 = P2 + 1/2pv2

2 + pgh2

• When the fluid isn’t moving this gives the pressure equation P = Po + pgh

• This equation is used often to explain the affects of moving air like wind over a roof.